DOCUMENTATION OF OSE TAOS AREA CALIBRATED GROUNDWATER FLOW MODEL T17.0 1/11/2006

Transcription

1 Attachment 3 to the SETTLEMENT AGREEMENT AMONG THE UNITED STATES OF AMERICA, TAOS PUEBLO, THE STATE OF NEW MEXICO, THE TAOS VALLEY ACEQUIA ASSOCIATION AND ITS 55 MEMBER ACEQUIAS, THE TOWN OF TAOS, EL PRADO WATER AND SANITATION DISTRICT, AND THE 12 TAOS AREA MUTUAL DOMESTIC WATER CONSUMERS ASSOCIATIONS Part I: Documentation of OSE Taos Area Calibrated Groundwater Flow Model T17.0, January 11, 2006, by Peggy Barroll, PhD and Peter Burck, CGWP, NMOSE. 37 pages, plus Appendices A, B and C. Part II: Development of the T17sup.M7 Superposition Version of the Taos Area Groundwater Model, and Water Rights Administration under the Taos (Abeyta) Settlement; April 16, by Peggy Barroll, PhD, NM OSE. 17 pages, plus Appendices A, B, C, D and E.

2 Attachment 3 Part I Documentation of OSE Taos Area Calibrated Groundwater Flow Model T17.0, January 11, 2006, by Peggy Barroll, PhD and Peter Burck, CGWP, NMOSE. 37 pages, plux Appendices A, B and C.

3 DOCUMENTATION OF OSE TAOS AREA CALIBRATED GROUNDWATER FLOW MODEL T17.0 1/11/2006 by Peggy Barroll, Ph.D. and Peter Burck, CGWP New Mexico Office of the State Engineer with Taos Area Hydrogeologic Framework Discussion and Attachment by Paul Drakos, Jay Lazarus, Mustafa Chudnoff and Meghan Hodgins of Glorieta Geoscience Inc. Prepared by the New Mexico Office of the State Engineer Water Resource Allocation Program Technical Services Division

4 TABLE OF CONTENTS Page Executive Summary Introduction Project Overview Code and Software Modeled Area Conceptual Model Stream-Aquifer Interaction Hydrogeology. 7 2 Groundwater Model Design and Input Parameters Model Temporal Discretization Model Structure Areal Recharge and Mountain Front Recharge Irrigation Return Flows Surface Water Features Evapotranspiration Groundwater Diversions Hydraulic Properties Model Calibration Calibration Overview Calibration Targets Calibration Results Summary and Conclusions 22 5 References.. 23 Figures Appendix A: Water Level Data for Calibration Appendix B: Distribution of Hydraulic Properties, Stresses and Calibration Results Appendix C: Hydrologic Characteristic of Basin-Fill Aquifers in the Southern San Luis Basin, New Mexico by Paul Drakos, Jay Lazarus, Bill White, Chris Banet, Meghan Hodgins, Jim Riesterer and John Sandoval, Appendix D: CD with T17.0 Model Input Files: Calibrated Model and Future Projection Input Files. ii

5 LIST OF FIGURES Figures follow text: pages Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Location map Observed water-level contour map (after Spiegel and Couse, 1969; and Purtymun, 1969), with new exploration wells posted. Model grid and selected model boundary features superimposed on base map. Model grid, selected model features with information on upper-most active model layer, and stream reach identifiers. Schematic cross section of the Taos Valley showing geological layers represented in the Taos Groundwater model. Cross-section, to scale, but with vertical exaggeration, showing model layers with topography and water table superimposed. Enlarged cross-section, to scale, but with vertical exaggeration, showing model layers with topography and water table superimposed. Enlarged to show uppermost layers in more detail. Calibration Results for Taos Groundwater Model: All head observations plotted vs. simulated heads. A perfect model would have all points landing on the 1:1 line (shown). Calibration Results for Taos Groundwater Model: Frequency Distribution of Residuals: Residual = observed head minus simulated head. Diagram of Model Grid with Vertical Hydrologic Gradient Sites. iii

6 LIST OF TABLES Table Table 1 Participating Member of Taos Technical Committee 2 Table 2 Model Layer Descriptions 10 Table 3 Transmissivity and Storage Values from Pumping Tests 17 Table 4 Model Calibration Statistics 20 Table 5 Vertical Head Differences between Shallow and Deep Wells: Observed and Simulated. Table 6 Model Water Budget 22 Page 21 iv

7 EXECUTIVE SUMMARY A calibrated groundwater model has been developed for the Taos Valley. This model is the result of several years of collaboration between the NM Office of the State Engineer, the U.S. Bureau of Reclamation, and other professional hydrologists with considerable experience in the Taos Valley, representing the Parties to the Abeyta Adjudication Settlement negotiations. The model was developed in response to 1) a need for a tool to evaluate the effects of groundwater development proposed during Adjudication Settlement Negotiations, especially groundwater diversions from deep levels of the aquifer system, and 2) a need for a tool to administer the wells subject to the Settlement Agreement. Given the hydrogeologic complexity of the Taos area, this groundwater flow model does a relatively good job matching observed water levels, the discharge from the springs at Buffalo Pasture, and the observed large downward vertical gradients. Simulation of the large vertical gradients constrains model vertical anisotropy, and allows the model to simulate the interaction between the deep and shallow aquifer systems with reasonable reliability. The model was designed, in part, to evaluate the hydrologic effects of wells proposed under the Taos Adjudication settlement, and it is recommended that the model be used in evaluating the hydrologic impacts of those wells. Determination of how and whether the model should be applied to the hydrologic evaluation of other wells should be made on a case-by-case basis. 1. INTRODUCTION 1.1 Project Overview At the request of the Parties to the Abeyta Adjudication Settlement negotiations, the New Mexico Office of the State Engineer (OSE) Hydrology Bureau developed a regional, 7-layer, groundwater flow model of the Taos Valley, New Mexico using the USGS groundwater flow simulator MODFLOW The OSE developed the model with input from members of the Taos Technical Committee. (Table 1) The Taos Technical Committee is comprised of geohydrologists representing the major parties involved in Taos Settlement negotiations (State of New Mexico ex rel. State Engineer v. 1

8 Abeyta and State of New Mexico ex rel. State Engineer v. Arellano, Civil Nos BB and 7939-BB (consolidated) ( Abeyta )). Numerous model versions were generated during this process. This report documents the version released in 2004 as version T17.0, which was adopted by the Parties to the settlement negotiations for the purpose of evaluating hydrologic aspects of the Settlement Agreement. Table 1 Participating Members of Taos Technical Committee Names From Party Represented Peggy Barroll NM Office of the State State of New Mexico Peter Burck Engineer (OSE) Robert Talbot US Bureau of Reclamation United States Tom Bellinger (USBOR) Lee Wilson Lee Wilson and Associates Taos Pueblo Roger Miller Mustafa Chudnoff Jay Lazarus Glorieta Geoscience Town of Taos Meghan Hodgins Paul Drakos John Shomaker John Shomaker and Associates, Inc. Taos Valley Acequia Association Maryann Wasiolek Michael Spinks Hydroscience Associates Inc. El Prado Water and Sanitation District Chris Banet Bill White John Sandoval US Bureau of Indian Affairs (USBIA) Taos Pueblo This model incorporates results from recent hydrogeologic investigations, including a recent Town of Taos/Taos Pueblo cooperative deep drilling and hydrologic testing project sponsored by the USBOR. The geologic and hydrogeologic framework and aquifer coefficients used in the model are presented in Drakos et al. (2004c), which summarizes and interprets results from the deep drilling program and other Taos Valley geologic and hydrologic investigations. The Drakos Report is presented in Appendix C of this report. The model also incorporates the most recent geologic/hydrologic mapping by the New Mexico Bureau of Geology and Mineral Resources. Water level data collected by many agencies and consultants were used as calibration targets, including new data from the deep drilling project that allowed quantification of the large vertical hydraulic gradients present in the valley. The model simulates groundwater flow in about 3000 feet of alluvial and volcanic materials. Geologic strata represented in the model include Quaternary alluvial fan 2

9 deposits, Tertiary Servilleta basalt flows, and Tertiary Santa Fe Group sediments. Key hydrologic processes are simulated, including natural recharge, irrigation seepage, evapotranspiration, and the interaction between groundwater and surface water features including the Rio Grande, its tributaries, and Buffalo Pasture springs. The groundwater model is designed to calculate the effects of groundwater diversions on aquifer water levels and depletion to the Rio Grande, its tributaries and springs, including the Buffalo Pasture springs on Taos Pueblo. The tributaries supply water for irrigation to Taos Pueblo and to members of the Taos Valley Acequia Association. The Buffalo Pasture springs have great cultural significance to Taos Pueblo, and the Pueblo places a high value on protecting these springs. The groundwater model can be and has been used to evaluate scenarios in settlement negotiations in the on-going Abeyta water rights adjudication. In addition, it is anticipated that the model will form the basis of an administrative tool that will be used, as appropriate on a case-by-case basis, to administer water rights and evaluate the hydrologic impacts of proposed groundwater diversions, especially deep groundwater diversion such as the wells proposed in the Taos Settlement Agreement as of October (It may be preferable to use other methods to evaluate the effects of shallow wells). The model was run in steady state mode using long-term average stress inputs, and calibrated to the measured water levels from area wells and groundwater discharge estimated to occur to the Rio Grande and Buffalo Pasture. The calibrated model simulates observed heads and groundwater discharges reasonably well, and captures major groundwater features such as large downward vertical gradients, thus allowing the interaction of the shallow and deep aquifer systems to be well simulated. Transient calibration runs were made using historical metered and estimated groundwater diversions. These transient runs gave reasonable results, but groundwater development in the area has so far been very limited, and the available data do not show any significant aquifer response to groundwater development. This model was developed in conjunction with a surface water model of the Taos Valley that was produced by the USBOR. The development of the surface water model assisted in the development of some groundwater model input parameters, such as irrigation return flow and evapotranspiration by riparian and wetlands vegetation. 3

10 However, now that these basic inputs have been developed, no other data from the surface water model are required in order to evaluate groundwater diversions. The groundwater model can be run independently of the surface water model in the evaluation of development alternatives. 1.2 Code and Software The model was constructed using the modular three-dimensional finite-difference groundwater flow code developed by the United States Geological Survey (USGS) commonly known as MODFLOW (McDonald and Harbaugh, 1988, and Harbaugh and McDonald, 1996). MODFLOW-2000 was used in this application (Harbaugh et al., 2000; Hill et al., 2000). The model uses days (d) for the time unit, and the length units are in feet (ft). Thus, head measurements are given in feet above mean sea level (amsl), transmissivity values are in feet squared per day (ft 2 /d), and flow values are reported in cubic feet per day (ft 3 /d). 1.3 Modeled Area This model simulates the alluvial/volcanic aquifer system within the Taos Valley in Northern New Mexico (Figure 1). A detailed description of the model structure is presented in Section 2.2. The model is bounded by the mountain-front of the Sangre de Cristo Mountains on the east, the Rio Grande on the west, and the Rio Hondo on the north. The southern boundary is defined by the foothills of the Picuris Mountains and the confluence of the Rio Grande and Rio Pueblo de Taos (Figure 2). The model area includes the areas in and near the Town of Taos, Taos Pueblo, and surrounding communities (e.g., Ranchos de Taos, Los Cordovas, Cañon, Talpa, El Prado, Arroyo Seco, and Arroyo Hondo). The model grid is shown in Figure 3 and Conceptual Model The Taos Valley surface water system (Figure 2) consists of the Rio Grande and a number of tributaries that rise in the Sangre de Cristo Mountains and discharge into the Rio Grande. These tributaries include, from north to south, the Rio Hondo, Arroyo Seco, Rio Lucero, Rio Pueblo de Taos, Rio Fernando, Rio Chiquito and Rio Grande del 4

11 Rancho. The Rio Grande is deeply incised into the Servilleta basalts at the bottom of the Taos Gorge, and the tributaries generally become more deeply incised close to their confluence with the Rio Grande. Recharge enters the Taos groundwater system from 1) precipitation in the Sangre de Cristo Mountains, 2) seepage of tributary flow, 3) local precipitation, and 4) return flow and seepage from surface water irrigation. In general, groundwater in the shallow combined Servilleta/alluvial aquifer system flows in a southwesterly direction from the Sangre de Cristo mountain-front, subsequently discharging into the Rio Grande (Drakos et al. 2004c Figure 5). Based on limited data available from 12 deep wells (Drakos et al 2004c Figure 6), groundwater in the deeper alluvial aquifer, below the Servilleta basalts, appears to flow from east to west. Water leaves the aquifer via discharge to surface water features, pumping, and evapotranspiration. There may be some underflow components to and from adjacent basins, but these are not well quantified, and have been neglected in the current analysis. A schematic cross-section of the Taos Valley showing geologic layers represented in the model is presented in Figure 5. The model area includes a shallow unconfined alluvial aquifer system in the eastern part of the Taos Valley, underlain by layers of Servilleta basalt that extend westward to the Rio Grande. Below the Servilleta basalts, a deep aquifer system consisting of older Santa Fe Group basin fill deposits extends to depths greater than 3000 feet. Large downward gradients are observed between the shallow and deep systems, reflecting the drainage of groundwater from the shallow aquifer system downward into the deep aquifer. Within the deep system itself, piezometer data from the deep drilling project indicates moderate vertical gradients, mostly downward, but data from two sites indicates modest upward gradients (Drakos et al., 2004c). Groundwater development in the Taos Valley has been minor. On the order 2,500 acre-feet per year (AF/yr) of groundwater is diverted from wells, and the available water level data do not shown any significant or regional drawdown in response to this diversion. The few wells for which more than one water level is available do not show any systematic response to regional pumping, but rather, water level variations appear to reflect seasonal changes in conditions (USBIA wells near the Buffalo Pasture), or the difference in recharge between wet and dry years. 5

12 A number of springs discharge groundwater in the upper Taos Valley (within a few miles of the mountain front, where the water table is relatively shallow). The most significant of these are associated with the Buffalo Pasture on Taos Pueblo. Much of the spring discharge in the Taos valley appears to represent reappearing surface water that had seeped into the ground upstream of the springs, from streams, acequias or applied irrigation water. Evapotranspiration from phreatophytic vegetation and wetlands consumes water in some parts of Taos Valley, most significantly in the vicinity of the Buffalo Pasture. Evapotranspiration along the edges of streams probably intercepts infiltrating surface water before it could reach the regional water table, whereas wetlands farther away from streams are assumed to directly deplete shallow groundwater. 1.5 Stream-Aquifer Interaction The Rio Grande gains water throughout the river reach downstream of the Rio Hondo to the confluence of the Rio Grande and the Rio Pueblo de Taos, and acts as a drain to the groundwater system. Gains from groundwater seepage to the Rio Grande include subsurface gains along the riverbed and gains from springs in the canyon walls. Seepage studies and evaluation of gage data indicate that this reach gains about 20 to 25 cubic feet per second from groundwater (cfs) (Tetra Tech, 2003). The Rio Grande in this reach also gains water from surface inflows from the Rio Hondo and the Rio Pueblo de Taos. The tributary streams in the Taos area vary in how well they are connected to the groundwater system. The upper Rio Pueblo de Taos, near Taos Pueblo, is known to gain water from the groundwater system, as do various sub-reaches of the Rio Pueblo and Rio Lucero (USBOR, 2002). These reaches are clearly connected to the shallow groundwater system, and groundwater pumping could intercept water that otherwise would have discharged into these reaches. Other tributary reaches are unlikely to be well connected to the groundwater system. Except in its uppermost reaches at or near the mountain front, Arroyo Seco is a losing stream that is often dry, with lengthy reaches perched well above the water table. As a result, the connection between Arroyo Seco and the groundwater system is limited. Similarly, Rio Lucero above the Buffalo Pasture 6

13 is a losing stream that appears to be perched well above the water table; therefore groundwater pumping would not affect surface water flow in that reach. There are fewer observational data available for other tributary reaches such as the Rio Fernando, Rio Grande del Rancho and Rio Chiquito. It is assumed in the model that t these streams are connected to the groundwater system. The Buffalo Pasture itself is a large wetland located in and around the lower Rio Lucero, upstream from its confluence with the Rio Pueblo de Taos. The Buffalo Pasture is fed by the discharge of groundwater at numerous springs. Total groundwater discharge from the Buffalo Pasture appears to vary, and measurements and estimates of this discharge range from 2 to 15 cfs. In 2001, the total discharge measured from several large springs in the Buffalo Pasture totaled 7.41 cfs (USBOR, 2001). It is likely that much of the groundwater discharge from the Buffalo Pasture originated as seepage from the Rio Lucero and upstream acequias and also from mountain front recharge. The location of the springs may be geologically controlled: a low-permeability sedimentary unit may occur close to the surface under the Buffalo Pasture, forcing groundwater to the surface (Chris Banet, USBIA, personal communication, 8/22/2003). 1.6 Hydrogeology The Taos region is known to have at least four discrete groundwater zones or layers within 2500 feet below land surface. Figure 5 is a schematic cross section of the model area. There appear to be at least two water-bearing zones within the alluvial fan sediments above the Pliocene Servilleta basalt, one at depths approximately from 5 to 200 feet and another at depths approximately from 400 to 750 feet. Water in the fan sediments is sometimes perched and may be widespread across the eastern part of the valley as a result of historic irrigation practices. A third water-producing interval is located between the Upper and Middle Servilleta basalts and is informally referred to as the Aqua Azul Aquifer (Drakos, 2004a). The thickness of the entire Servilleta Formation (including interbedded sediments) ranges from 0 to 650 ft (Dungan et al., 1984). The sediments below the Servilleta are correlated with Miocene Santa Fe Group clays, silts, sands and gravels exposed in outcrop near Pilar, NM. These materials are rift fill sediments (Galusha and Blick, 1971) and consist of moderate to poorly sorted sands 7

14 with clasts of intermediate volcanic rock, quartzite, and other metamorphic rocks (Bauer and Kelson, 1998). Groundwater generally flows from recharge areas near the Sangre de Cristo Mountains westward toward the Rio Grande. In the eastern part of the Valley, the water table is well above the Servilleta basalts in shallow alluvial deposits only tens of feet below the surface. Farther west the water table is 150 ft or deeper within the Servilleta basalts and interbedded sediments. These geologic units are crosscut by numerous faults, generally associated with the development of the Rio Grande Rift. The faults generally trend north-south, and step down toward the west. Pumping test data from wells near these faults (part of the recent USBOR drilling program) indicate that some faults act as a partial barrier to the flow of groundwater (Drakos et al., 2004c). The Sangre de Cristo mountain block east of the Taos Valley has significantly different lithologic and hydrologic properties than the shallow alluvial or deeper basin fill aquifers. The mountain block is comprised of Paleozoic sedimentary rocks, Oligocene intrusives, and Precambrian granites. Groundwater flow within the mountain block is assumed to be small, and its effects are simulated in the model by a mountain front recharge term. To the north and south, the valley is constricted by the mountains and foothills. There may be some subsurface hydrologic connection between the Taos Valley and other valleys along the Rio Grande to the north and south, but these connections are poorly understood and not quantified. West of the Rio Grande, data are sparse and the hydrology is relatively poorly understood. 8

15 2. GROUNDWATER MODEL DESIGN AND INPUT PARAMETERS 2.1 Model Temporal Discretization The model was first run in steady-state mode using long-term averages of natural recharge and irrigation related return flow, and long-term average surface inflows to tributary streams. A 40-year transient run followed, in which the average recharge and stream-inflows from the steady-state run were continued, with the addition of increasing historically metered and estimated groundwater diversions. Relatively little groundwater development has occurred in the Taos Valley and a trend of declining water levels in response to groundwater development has not been observed. Therefore the most important and reliable part of the calibration is the steady-state run. The transient run was made to confirm that simulated water levels remained relatively stable, and are consistent with historically observed water levels. 2.2 Model Structure As shown in Figures 3 and 4, the model grid encompasses a 225-square mile area from the Rio Grande on the west, to the Taos range of the Sangre de Cristo Mountains on the east, and from the Rio Hondo on the north, to the confluence of the Rio Grande with the Rio Pueblo de Taos on the south. The model area measures 15 miles by 15 miles and has 60 rows, 60 columns, and 7 layers. Rows and columns are evenly spaced and measure 1,320 feet (1/4 of a mile) on each side. The southwest corner of the model grid is tied to the southwest corner of Section 2 of Township 24 North, Range 11 East, New Mexico Coordinate System. The grid is oriented northsouth and east-west. Figures 3 and 4 show the extent of the hydrologically active model cells, and some of the model boundary conditions. Model cells located in the mountain areas to the east and the area west of the Rio Grande are inactive. The lateral boundaries of the model are all specified flux and no-flow boundaries. These boundaries were not simulated as head-dependent-flux boundaries because of the lack of hydrologic information about how, or even whether, the Taos Valley aquifers extend continuously 9

16 beyond the boundaries here defined, and therefore it was decided that groundwater flow across those boundaries should be strictly limited. Figure 5 depicts a schematic geologic cross section of the model area. Layer descriptions and nominal thickness are given in Table 2. Figures 6 and 7 show a cross section of the model grid itself, with the observed water table superimposed. The total model thickness is more than 3,000 feet. Land surface elevations range from about 6,100 feet amsl in the southwest to just under 8,000 feet in the northeast. Upper layers thin and pinch out toward the west (Figure 5, 6 and 7). Consequently, rivers and streams cut down from higher to lower layers as they flow west. Figure 4 shows a plan view of the model, with the uppermost active layers of the model designated by color. LAYER 1, , 7 TABLE 2. MODEL LAYER DESCRIPTIONS GEOLOGIC DESCRIPTION Youngest alluvial fan deposits derived from Sangre de Cristo Mountains.. Youngest alluvial fan deposits derived from Sangre de Cristo Mountains. (Northern Basin: Reworked alluvial fan materials) Reworked alluvial fan materials and other basin fill deposits including poorly to well sorted silts, sands, and gravels THICKNESSES (ft) 20, (up to 700) <100 to 550 Pliocene Servilleta basalt flows and interbedded sediments 400 Miocene Santa Fe Group sediments composed of fluvial, eolian, and lacustrine clays, silts, sands, and gravels 500, 1700 For reasons of model stability, the model simulates all layers as Type 0 layers, in which transmissivity does not change as aquifer water levels change. MODFLOW requires input of aquifer storativity, and for the parts of Taos model layers that are unconfined, storativity values are set so that appropriate unconfined storages are calculated. The assumption of constant transmissivity layers is acceptable since historical drawdowns have been very small, and anticipated drawdowns in the shallow unconfined system are anticipated to remain small. Geologic deposits simulated include Quaternary alluvial fan materials derived from the Taos Range of the Sangre de Cristo Mountains (Layers 1 through 4), Pliocene Servilleta basalt flows and interbedded sediments (Layer 5), and Miocene Santa Fe 10

17 Group sediments consisting of clay, silt, sand, and gravel of fluvial, aeolian, and lacustrine origin (Layer 6 and 7). Several mapped faults are represented using the MODFLOW horizontal flow barrier (HFB) package. These faults Los Cordovas, Town Yard, and other unnamed faults generally trend north and are typically down to the west. Two types of faults, out of numerous mapped faults, were explicitly simulated with the MODFLOW HFB package: 1) faults for which water level and pumping test data suggest a hydrologic influence (Drakos, et al, 2004c) and 2) a number of other representative major faults. The faults were simulated as less transmissive than the surrounding aquifer material, thereby slowing the east-west flow of groundwater in the deeper layers. 2.3 Areal Recharge and Mountain Front Recharge Areal recharge is estimated at 4% of the average annual precipitation (12.55 inches per year, Garrabrant, 1993) or 0.5 inches. Areal recharge is simulated with the MODFLOW recharge package and is distributed uniformly over the uppermost active cells in model layers 1 through 4, where the water table is within ~200 feet of the surface. The total amount of areal recharge applied is 1,820 acre-feet per year. Mountain front recharge of about 5,310 acre-feet per year is applied along the mountain front on the eastern and part of the southern boundary (see diagram in Appendix B), through the MODFLOW WEL package, which applies specified flux stresses to the groundwater system. The amount of mountain front recharge was originally based on discussions with the Taos Technical Committee and water budget calculation for the area (Keller and Blisner, 1995), and modified during calibration to improve the agreement between simulated and observed water levels and groundwater discharge. The final amount of mountain front recharge (5,310 acre-feet per year) is equal to about 1.3% of the estimated average annual precipitation over the mountainous part of the watershed, which is not inconsistent with results obtained by the USGS using chloride mass balance methods for other watersheds in the Sandia (0.7% to 15 %) and Sangre de Cristo (3% to 6%) Mountains (Anderholm 2001 and 1994), although it is on the low side. In comparison, surface water runoff represents about 23% of the estimated mean annual precipitation in the mountainous part of the 11

18 watershed. The distribution of mountain front recharge in the model area was originally based on a water budget study by Mike Johnson (2003) and modified during calibration. Mountain front recharge is applied in model layers 1 through 4, at rates decreasing with depth, to represent both infiltration of streamflow at the mountain-front, and smaller amounts of deeper flow from the mountain-block. 2.4 Irrigation Return Flows Irrigation return flows consist of recharge from acequia/ditch/lateral seepage and on-farm deep percolation. The amount and distribution of the return flow referred to as groundwater accretions was derived from the U.S. Bureau of Reclamation s Taos Valley surface water model (Bellinger, 2003). Groundwater accretions represent a fraction of the surface water diverted for irrigation of about 12,000 acres of land (Bellinger, 2003). The surface water model calculates groundwater accretions on a seasonal basis for a variety of surface water reaches. These reaches were correlated with zones of cells in the groundwater model corresponding to the locations of the conveyances and irrigated lands. A long-term average of the groundwater accretions from the surface water model was applied to the groundwater model, on a zone-by-zone basis (see diagram in Appendix B). Groundwater accretions include only the part of irrigation return flows that actually recharge the regional aquifer. Groundwater accretions do not include excess irrigation water that remains on the surface or that only seeps into the shallow subsurface and quickly reappears as surface water. Such water is treated in the surface water model as being available to downstream irrigators. The groundwater accretion components were applied in zones defined using Geographic Information System (GIS) coverage identifying irrigated lands. Specified flux cells in the MODFLOW WEL package were used to simulate this process. Groundwater accretions account for a total of about 11,910 AFY, reflecting about 1 AFY of deep percolation to the aquifer per acre of irrigated land resulting from both canal seepage and on-farm return flows. 12

19 2.5 Surface Water Features Eight river reaches are simulated in the model: Rio Grande Rio Hondo Arroyo Seco Rio Lucero Rio Pueblo de Taos Rio Fernando de Taos Rio Chiquito, and Rio Grande del Rancho. The Rio Grande is simulated using the RIV package of MODFLOW, and the tributaries are simulated using the STR package. The RIV package simulates headdependent flux to and from the groundwater from a simple surface water body. The STR package is a more complex version of RIV that allows for some accounting of the amount of surface water in the tributaries, and allows the tributaries to go dry when all the surface water is lost. Long-term average annual stream flow values derived from USGS stream gage measurements are applied to the upper end of the tributary STR cells. Since the Rio Grande is perennial and gaining in this reach, it was decided that it was not necessary to use the more complex STR package to simulate the Rio Grande. The model is designed such that the various reaches incise more deeply into the model from east to west. That is, the upper (eastern) portions of the tributaries are simulated by cells in layers 1 through 3, farther west these tributaries drop into layers 4 and 5, and the Rio Grande itself is in layers 5 and 6. The Buffalo Pasture springs cover a roughly 600-acre marshy area on both sides of the Rio Lucero. These springs are represented as cells in two reaches of the Rio Lucero using MODFLOW STR package. Input elevations associated with all STR and RIV cells were determined from USGS Digital Elevation Model data and from topographic maps. Conductances for tributary STR cells were initially set assuming a vertical hydraulic conductance of about 1 ft/d, and modified slightly during calibration. Final conductance values for most of the tributary reaches ranged from 10,000 to 50,000 ft 2 /d. The conductances of cells 13

20 representing the heart of the Buffalo Pasture were much higher in order to represent the large area of groundwater discharge, and to simulate the observed spring discharge. The final conductance value for cells in the heart of the Buffalo Pasture was 500,000 ft 2 /d. The RIV cells representing the Rio Grande were also given large conductances (550,000 ft 2 /d), representing the high degree of hydrologic connection that exists between the Rio Grande and the geologic units which discharge into it. 2.6 Evapotranspiration Non-crop evapotranspiration (ET) is simulated with the MODFLOW ET package. The ET package was applied to all of the uppermost active cells of the model, but an extinction depth of 6 feet was specified, which meant that ET was only active in a limited part of the model. In most cells, a maximum evaporation rate of 2.2 feet per year was specified based on calculation of CIR for phreatophytes made by Brian Wilson of the OSE (Wilson and Smith, 2004). In cells containing stream reaches, the maximum ET rate is reduced to one-fifth of that in other cells. This reduction is made in stream cells to account for the fact that much of the water consumed by stream-side vegetation is probably intercepted surface water, a physical process which is accounted for in the water budget of the USBOR surface water model. Total ET from the groundwater model is simulated to be about 5,370 acre-feet per year, which is a reasonable value consistent with other estimates of non-crop evapotranspiration, but not well constrained by observational measurements. A comparison of spatial locations of model cells experiencing ET with GIS coverage of soggy soils/wet meadows (from the National Resources Conservation Service Soil Survey Geographic Database, SSURGO) shows relatively good agreement between the two 1. 1 The best available information regarding locations where ET actually occurs in the field is reportedly the SSURGO data, which shows the spatial distribution of soils that developed under anoxic conditions because of perennial or seasonal high water levels, and also soils that occur in association with hydric conditions on the loosely defined valley floors (Roger Miller, personal communication, 7/29/2003). 14

21 2.7 Groundwater Diversions Groundwater diversions from a variety of water users are represented (see diagrams in Appendix B). The model includes the following groundwater diversions (with recent diversion amounts): 1) Town of Taos municipal wells (currently about 840 acre-feet per year), 2) El Prado Water and Sanitation District (64 acre-feet per year), 3) about one dozen mutual domestic water users associations (about 400 acrefeet per year) 4) approximately 1,900 individual private domestic wells (pumping 560 acre-feet per year), 5) multiple household domestic wells (pumping 300 acre-feet per year), and 6) commercial sanitary wells using 190 acre-feet per year. Wells were identified from OSE records and by data provided by Taos Technical Committee members. Metered diversions were available for public water supply wells. Diversions for other wells were estimated at 0.25 AFY per well for domestic wells serving single dwellings, 3.0 AFY per well for domestic wells serving multiple dwellings, and 3.0 AFY for wells listed in OSE records as Sanitary type wells. 2.8 Hydraulic Properties The model defines zones of hydraulic conductivity (K), which are then multiplied by layer thicknesses (b) to generate transmissivity. Model hydraulic conductivities were in part defined based upon the results of 46 aquifer tests (Drakos et al. 2004c, Tables 1, 2, 3, 4, 5; Table 3 this report), and in part based on available lithologic data. Adjustments were made to both K values in zones and the boundaries between zones during calibration, while keeping model values consistent with the magnitude and trends of the available well test data. Transmissivity (T) values from aquifer tests in the shallow system range from 250 to 6,000 ft 2 /d although no values are available for the shallowest stream-channel sediments. Transmissivity in the lower aquifer system tends to be lower, ranging from 100 to 1,600 ft 2 /d. 15

22 The final hydraulic conductivities in the calibrated model produce T values that are consistent in trend and magnitude with the aquifer test values (see diagrams in Appendix B). Model hydraulic conductivities in the shallow system range from 1.0 to 90.0 ft/d, yielding T values in the range from 500 to 10,000 ft 2 /d. A very low K and T are given to cells within Buffalo Pasture, representing low permeability Marsh sediments, and the underlying Blueberry Hill deposit, which are thought to force groundwater to discharge in this area (verbal communication, Chris Banet, US BIA). Model hydraulic conductivities for the deeper layers (6 and 7) are systematically lower, ranging from 0.1 to 3.0 ft/d, yielding T values of around 200 to 400 ft 2 /d in the central part of the Taos Valley, and T values between 1,000 and 2,500 ft 2 /d for the western and southern parts of the deep system. The higher values of T in the western part of layers 6 and 7 are consistent with an aquifer test from the River View Acres well of 1250 ft 2 /d, near the Rio Grande, but are otherwise poorly constrained by well test data. There are few pumping tests with observation wells in the shallow aquifer in the Taos area. Therefore, storage values for the Taos model were based on standard hydrologic texts (Freeze and Cherry, 1979) and other alluvial aquifer models in New Mexico (McAda and Barroll, 2002; McAda and Wasiolek, 1988). For reasons of stability, the model simulates all layers as Type 0, in which a specific storage value is multiplied by the layer thickness. Specific storage was set so as to generate the appropriate unconfined storage coefficient (0.15) for areas that are not confined. That is, specific storage for each cell is set equal to 0.15 divided by the saturated thickness of the cell. For parts of the model that are confined, the specific storage is set at 2 x 10-6 per foot, which is consistent with the theoretical storage due to the compressibility of water with adjustment for aquifer compressibility, and consistent with other water resource groundwater models of alluvial basins (McAda and Barroll, 2002). There is evidence that the vertical anisotropy (the ratio of horizontal hydraulic conductivity to vertical) is large. This evidence includes the presence of 1) large observed vertical hydraulic gradients (up to 50 feet of head decline per 100 feet of increasing depth), and 2) horizontal low permeability beds, including thick horizontal basalt layers. Model anisotropy was determined during calibration, in order to accurately simulate the observed vertical gradients, and ranges from 25:1 near the edges of certain alluvial layers, to 1400:1 in the basalt layer. 16

23 Table 3 Transmissivity and Storage Values from Pumping Tests Well Name Screened Depth Transmissivity (ft 2 /d) Storage (unitless) Arroyo Park Shallow Baird Joint Venture Shallow Barranca del Pueblo Shallow BOR 2A Shallow 230 Buffalo Pasture Shallow Cameron Shallow Ceja de Colonias Shallow Cielo Azul Shallow 390 Clinic Shallow 900 Colonias Point Shallow Cooper Shallow Don s Shallow 810 Hail Creek Deep Shallow Howell Well Shallow Kit Carson Shallow La Fontana Shallow La Percha Shallow Riverbend Shallow River View Acres Shallow 1250 San Juan-Chama Shallow Ski & Tennis Ranch Shallow TP-2 Taos North Shallow 930 Tract A PW2 Shallow 175 El Prado Shallow+Deep 3000 Airport Deep Deep est. 250 BOR 1 (RG-73095) Deep BOR 2B Deep BOR 2C Deep BOR 3 (RG EX) Deep BOR 4 Deep BOR 5 Deep BOR 6 Deep BOR 7 Deep 109 Karavas 2 (Screen 2) Deep Karavas 3 Deep Mariposa Deep 530 National Guard Domestic Deep 760 Rio Pueblo 2000 Deep Rio Pueblo 2500 Deep Taos Yard Deep 400 Tract A PW Deep 300 Tract B PW Deep Tract B PW2 Deep 220 Tract B Tip BIA 10 Deep Tract B Tip BIA 11 Deep 310 UNM Taos Deep

24 3. MODEL CALIBRATION 3.1 Calibration Overview The model was started under steady-state conditions, which represented conditions before substantial groundwater pumping, followed by a transient historical period simulation of 40 years during which historical groundwater diversions were applied. The model was calibrated to observed water level data, estimated discharge from the Buffalo Pasture springs and discharge to the Rio Grande. Calibration was done using trial-and-error methods. Little change in model water levels or discharges was simulated to occur during the transient simulation in most areas of the model, which is consistent with the available observational data. Observed well hydrographs show only climatically induced variability, and not any trend indicative of groundwater development. Therefore, no attempt was made to simulate the observed well hydrographs; instead the simulated change in water levels over the transient period was checked to ensure that unreasonably large values had not been simulated. 3.2 Calibration Targets Water level data used to calibrate the model were obtained from various sources including: U.S. Geological Survey (USGS) Ground-Water Site Inventory (GWSI) Office of the State Engineer well records (including WATERS database) Bauer et al. (1999) Garrabrant (1993) Glorieta Geoscience, Inc. reports Lee Wilson and Associates, Inc. report (1978) Taos Pueblo well inventory Purtymun (1969) These water level data are tabulated in Appendix A. The range of water levels is similar to the range in land surface elevation in the model, from about 6,100 feet amsl at the Rio Grande to nearly 8,000 feet amsl near the mountain front. There is considerable scatter in the observed water level data, in part because of issues of hydrogeologic complexity and the presence of large hydrologic 18

25 gradients, but also in part because of variable data quality. The recent USBOR drilling program provides high quality data from a number of piezometer nests, allowing quantification of the vertical gradient. Calibration was performed so as to match both individual water levels and to match the overall large downward vertical gradient between the shallow and deep aquifer systems. No attempt was made to simulate the much smaller observed upward gradient within the deep aquifer, which is assumed to be associated with a local geologic structure (Drakos et al., 2004c). Additional calibration targets included groundwater discharge to the Rio Grande within the reach simulated by the model (estimated at about 1 cfs per mile or 20 cfs), the estimated discharge from the Buffalo Pasture (estimated at various times between 2 and 15 cfs), and the general distribution of gaining and losing reaches on the tributaries, including some seepage loss data from the Rio Lucero and Rio Pueblo de Taos. For convenience, water level targets and the discharge target for the Buffalo Pasture were including in MODFLOW-2000 observation package input files. MODFLOW-2000 automatically provided output on how well these targets were matched, which simplified evaluation of trial-and-error calibration runs. 3.3 Calibration Results Trial-and-error calibration resulted in a model whose hydraulic properties are relatively consistent with observed values, and that simulates observed water levels, vertical gradients and groundwater discharges adequately. The distribution of hydraulic properties in the calibrated model is provided Appendix B in diagram form. The match of simulated and observed water levels (also provided in Appendix B) is generally good, but shows considerable scatter, which is expected considering the large amount of scatter in the available water level data. In general, the shallow system is simulated more closely than the deep system. Model calibration statistics are given in Table 4. 50% of simulated water levels are within 20 feet of observed values, and 82% are within 50 feet, which is acceptable given the scatter in the data and the large range of observed water levels across the model area (1267 feet). Most large residuals are associated with wells at the edge of the basin, or wells of suspect location or screening (we did not attempt to eliminate such outliers). Figure 8 shows observed vs. modeled water level elevations, and Figure 9 is a chart of the distribution of residuals. The 19

26 residual is the difference between the observed head and the model simulated heads at the same locations (observed head minus model-simulated head). Ideally, for a perfect model, all residuals would be zero. Figures 8 and 9 show a reasonable distribution of residuals for a regional model of this complex system. Residuals are mostly of reasonable size, and their distribution is centered on zero. The fact that the upper model layers pinch out to the west as the water table cuts down through the geologic section causes some anomalous conditions at the limits of these layers. In the layers 1, 2 and 3 this is treated by increasing the vertical conductance at the western edge of the pinching layer, thus allowing water from an upper layer to flow westward, in accordance with the hydrologic gradient, into the next layer. This creates minor anomalies in simulated heads, especially near the western edge of layer 4 where simulated heads drop precipitously, creating more of a step than can be observed in field data. However, observed data are sparse in this area, west of Arroyo Seco, where the water table drops hundreds of feet below land surface as the shallow aquifer system gives way to a deeper hydrologic system. What data there are suggest that the shallow hydrologic system represented by model layers 1-4 may not be in direct connection with the deeper hydrologic system represented in layers 5, 6 and 7 in this area. Without more detailed local data it probably would not be worthwhile attempting to improve the simulation of this area. TABLE 4. Model Calibration Statistics PARAMETER ALL LAYERS Number of Observations 354 Residual Mean (feet) 0.95 Residual Standard Deviation (feet) 44.5 Sum of Squared Residuals (feet squared) 695,424 Absolute Residual Mean (feet) 30.0 Minimum Residual (feet) -143 Maximum Residual (feet) 229 Observed Head Range (feet) 1267 Minimum Observed Head (feet) 6452 Maximum Observed Head (feet) 7719 Std. Deviation/Head Range 3.5 % Percent of Residuals within % Percent of Residuals within % Percent of Residuals within % Percent of Residuals within % Percent of Residuals within % 20

27 This model closely simulates the large vertical gradients observed between the shallow (layers 1-4) and deep (layers 5-7) aquifer system in the Taos Valley. Observed difference in water level between deep and shallow wells and /or piezometers at the same location range from 100 to over 400 feet (the deeper well having the lower water level), and this phenomenon was well simulated by the model (see Table 5). These well-quantified downward vertical gradients constrained model vertical anisotropy, which in many models is a highly uncertain and unconstrained parameter because of the lack of definitive calibration data from multi-level piezometers. TABLE 5. Vertical Head Difference Between Shallow and Deep Wells and Corresponding Model Layers. All Gradients Listed Reflect Lower Heads at Deeper Depths WELL OBSERVED (feet) BOR 1/ National Guard BOR 2 and BOR 4 and BOR BOR Cielo Azul Grumpy 137 () 473 Karavas 2 and L25/L Rio Pueblo SIMULATED (feet) The groundwater model also adequately simulates observed groundwater discharge targets. Analysis of recorded flows in the Rio Grande from the confluence of the Rio Grande and Rio Hondo to the Taos Junction stream gage shows a gain of about cfs (or about 1 cfs per mile). The model simulates approximately 21 cfs discharge from groundwater in this reach. At the Buffalo Pasture, modeled discharge from groundwater is about 5 cfs or 3,800 acre-feet per year, compared with 2 to15 cfs range of observed discharge (which may contain a direct surface water return component not simulated here in the model). In addition, other qualitative flow and discharge targets were simulated successfully. These targets include large observed losses from the upper reach of the Rio Lucero and gains to the upper reach of the Rio Pueblo de Taos. Arroyo Seco was 21

28 also correctly simulated to have large losses, and as going dry over an extended reach. The water budget from the calibrated model at the end of the transient run is provided in Table 6. The difference between total recharge and total discharge is less than 0.05%, and is well within acceptable limits. TABLE 6. Groundwater Model Water Budget, End of Simulation (Present-Day Conditions) Recharge AF/Y Discharge AF/Y Areal Recharge from Precipitation 1,820 Discharge at Buffalo Pasture Springs 3,960 Mountain Front Recharge 5,310 Evapotranspiration 5,350 Irrigation Seepage 11,910 Groundwater Pumping 2,540 Tributary Recharge (to aquifer) 18,810 Discharge to Tributaries 11,420 Water Released from Aquifer 370 Discharge to Rio Grande 14,940 Storage Total Recharge 38,220 Total Discharge 38, SUMMARY, CONCLUSIONS, DISCUSSION The T17.0 model is the result of several years of collaboration between the OSE, and the US Bureau of Reclamation with input from other professional hydrologists with considerable experience in the Taos Valley representing the Parties to the Abeyta Adjudication Settlement negotiations. The model was developed in response to 1) a need for a tool to evaluate the effects of groundwater development proposed during Adjudication Settlement Negotiations, especially groundwater diversions from deep levels of the aquifer system, and 2) a need for a tool to administer the wells subject to the Settlement Agreement. New hydrologic data became available from a deep-drilling program funded by the U.S. Bureau of Reclamation, which was integral to the development of a regional model of the Taos Valley that provides reasonable and reliable results when simulating deep-aquifer pumping. Given the hydrogeologic complexity of the Taos area, this groundwater flow model does a relatively good job matching observed water levels, the discharge from the springs at Buffalo Pasture, and the observed large downward vertical gradients. Simulation of the large vertical gradients constrains model vertical anisotropy, and allows the model to simulate the interaction between the deep and shallow aquifer systems with reasonable reliability. This model provides reasonable and useful 22

29 predictions of the impacts of proposed wells. The model was designed, in part, to evaluate the hydrologic effects of wells proposed under the Taos Adjudication settlement, and it is recommended that the model be used in evaluating the hydrologic impacts of those wells. Determination of how and whether the model should be applied the hydrologic evaluation of other wells should be made on a case-by-case basis. 5. REFERENCES Anderholm, S.K., 1994, Groundwater Recharge near Santa Fe, North-central New Mexico. USGS Water-Resources Investigation Report Anderholm, S.K., 2001, Mountain-front Recharge Along the Eastern Side of the Middle Rio Grande Basin, Central New Mexico: USGS Water-Resources Investigations Report Banet, C., USBIA, personal communication, 8/22/2003 Bauer, P.W., Johnson, P.S., and Kelson, K.I., 1999, Geology and Hydrology of the Southern Taos Valley, Taos County, New Mexico, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM. Bauer, P., and Kelson, K., 1998, Geology of Ranchos de Taos Quadrangle, Taos County, New Mexico: New Mexico Bureau of Mines and Mineral Resources Open-file Digital Geologic Map OF-DGM 33. Bellinger, T.R., Taos Valley Surface Water Hydrologic Model Development and Baseline Results. Draft USBOR Technical Report, Denver Technical Center. Burck, P., Barroll, P., Core, A. and Rappuhn, D., 2004,. Taos Regional Groundwater Flow Model. New Mexico Geological Society Guidebook, 55 th Field Conference, Geology of the Taos Region, p Drakos, P., Lazarus, J., Riesterer, J., White, B., Banet, C., Hodgins, M., and Sandoval, J., 2004a. Subsurface Stratigraphy in the Southern San Luis Basin, New Mexico. New Mexico Geological Society Guidebook, 55 th Field Conference, Geology of the Taos Region, p Drakos, P., Sims, K., Riesterer, J., Blusztajn, J., Lazarus, J., 2004b. Chemical and Isotopic Constraints on Source-Waters and Connectivity of Basin-Fill Aquifers in the Southern San Luis Basin, New Mexico. New Mexico Geological Society Guidebook, 55 th Field Conference, Geology of the Taos Region, p

30 Drakos, P., Lazarus, J., White, B., Banet, C., Hodgins, M., Riesterer, J., and Sandoval, J., 2004c. Hydrologic Characteristics of Basin-Fill Aquifers in the Southern San Luis Basin, New Mexico. New Mexico Geological Society Guidebook, 55 th Field Conference, Geology of the Taos Region, p Dungan, M. A., Muehlberger, W.R., Leininger, L., Peterson, C., McMillan, N.J., Gunn, G., Lindstron, M., and Haskin, L., Volcanic and sedimentary stratigraphy of the Rio Grande gorge and the late Cenozoic geologic evolution of the southern San Luis Valley, in New Mexico Geological Society Guidebook 35 th Field Conference, Rio Grande Rift: Northern New Mexico, p Freeze, R.A. and Cherry, J.A., Groundwater. Prentice-Hall, Inc., Englewood Cliffs, N.J. 604 p. Galusha, T., and Blick, J., 1971, Stratigraphy of the Santa Fe Group, New Mexico: Bulletin of the American Museum of Natural History, v. 144, Article 1. Garrabrant, L.A., 1993, Water Resources of Taos County, New Mexico, U.S. Geological Survey Water-Resources Investigations Report , Albuquerque, NM. Glorieta Geoscience, Inc., June, 1991, Geohydrology of the Pinones de Taos, Taos County, New Mexico, Consultant Report prepared for Stephen Natelson and Fred Fair, OSE file copy. Glorieta Geoscience, Inc., March, 1995, Town of Taos San Juan/Chama Diversion Project Phase 2, Volume 1, Production Well and Observation Well Installation, Testing, and Determination of Aquifer Coefficients, Consultant Report prepared for the Town of Taos and Lawrence Ortega & Associates, OSE file copy. Glorieta Geoscience, Inc., August, 1997, Pumping Test Analysis, Arroyo Seco School Well, Taos County, New Mexico, Consultant Report prepared by Paul Drakos for Fennell Drilling Co., OSE file copy. Glorieta Geoscience, Inc., 2000, Drilling and Testing Report, Bureau of Reclamation 2000-Feet Deep Nested Piezometer/Exploratory Well (BOR #1), Taos, NM, Consultant Report prepared by Paul Drakos and Meghan Hodgins for the Town of Taos. Glorieta Geoscience, Inc., 2002, Drilling and Testing Report, Bureau of Reclamation 2000-Feet Deep Nested Piezometer/Exploratory Well (BOR #2), and 2100-Feet Deep Production Well (BOR #3) Paseo del Ca on West Site, Taos, NM, Consultant Report prepared by Paul Drakos and Meghan Hodgins for the Town of Taos. Harbaugh, A.W and M.G. McDonald, 1996, User s Documentation of MODFLOW-96, an update to the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model, U.S. Geological Survey Open-File Report , Reston, VA. 24

31 Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G., 2000, MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- User guide to modularization concepts and the Ground-Water Flow Process: U.S. Geological Survey Open-File Report 00-92, 121 p. Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, E.R., 2000, MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- User guide to the Observation, Sensitivity, and Parameter-Estimation Processes and three postprocessing programs, U.S. Geological Survey Open-File Report , 210 p. Johnson, M., Taos Groundwater Model Recharge Study. Internal OSE Draft Memorandum dated June 30, Keller and Bliesner, 1995, Taos Valley Water Balance ( ). 1 page table. McAda D.P., and Barroll, P., Simulation of Groundwater Flow in the Middle Rio Grande Basin between Cochiti and San Acacia, New Mexico. U.S. Geological Survey Water-Resources Investigations Report McAda D.P. and Wasiolek, M., 1988; Simulation of the Regional Geohydrology of the Tesuque Aquifer System near Santa Fe, New Mexico. U.S. Geological Survey Water-Resources Investigations Report McDonald, M.G. and A.W. Harbaugh, 1988, A Modular Three-Dimensional Finite- Difference Ground-Water Flow Model, Techniques of Water Resources Investigations of the United States Geological Survey, Book 6, Chapter A1, USGPO, Washington, D.C. Miller, R. Personal Communication, 7/29/2003. New Mexico Office of the State Engineer, 2000, Well Records stored in the Water Administration Technical Engineering Resource System (WATERS) Database. Purtymun, W.D., 1969, General ground-water conditions in Taos Pueblo, Tenorio Tract, and Taos Pueblo Tracts A and B, Taos County, New Mexico. US Department of the Interior, Geological Survey, Albuquerque, NM. Spiegel, Z. and Couse, I.W., 1969, Availability of groundwater for supplemental irrigation and municipal-industrial uses in the Taos Unit of the U.S. Bureau of Reclamation San-Juan Chama Project, Taos County, New Mexico. New Mexico State Engineer, Open-File Report, 22 p. Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Survey Geographic (SSURGO) Database for Taos County and Parts of Rio Arriba and Mora Counties, New Mexico. Available URL: " Accessed

32 Taos Federal Negotiation Team, undated, Hydrology and Water Management in the Taos Basin: A Guide for Decision-Makers. (Informally known as the Taos Data Book). Prepared in cooperation with Taos Pueblo, New Mexico State Engineer Office, Taos Valley Acequia Association, Town of Taos, New Mexico. Taos Pueblo Well Inventory, Provided by Chris Banet of the U.S. Bureau of Indian Affairs. Tetra Tech, Rio Grande Seepage Final Study Report, Taos Box Canyon, Report. Prepared for the U.S. Bureau of Reclamation USBR Contract No. 00-CA , Delivery Order 00-C , Dated April USBIA, 2001, U.S. Bureau of Indian Affairs, Site Completion Report for Subsurface Drilling, Sampling, and Testing of BOR #5 at West Deep Site, Taos Pueblo, Taos County, New Mexico. Prepared by USBIA, Southwest Regional Office (SWRO), Branch of Water Rights, Geohydrology Section. Prepared for Proposal for Technical Studies Conducted to Assist Settlement Discussions in the NM v. Abeyta, Drilling Program, Pueblo Portion, October USBIA, 2003, U.S. Bureau of Indian Affairs, BOR 4 Site Completion Report for the Pueblo Portion at Taos Pueblo, Taos County, New Mexico. Prepared by USBIA, Southwest Regional Office (SWRO), Branch of Water Rights, Geohydrology Section. Prepared for Proposal for Technical Studies Conducted to Assist Settlement Discussions in the NM v. Abeyta, Drilling Program, Pueblo Portion, March USBIA, 2003, U.S. Bureau of Indian Affairs, BOR 5 Site Completion Report for the Pueblo Portion at Taos Pueblo, Taos County, New Mexico. Prepared by USBIA, Southwest Regional Office (SWRO), Branch of Water Rights, Geohydrology Section. Prepared for Proposal for Technical Studies Conducted to Assist Settlement Discussions in the NM v. Abeyta, Drilling Program, Pueblo Portion, March USBIA, 2003, U.S. Bureau of Indian Affairs, BOR 6 Site Completion Report for the Pueblo Portion at Taos Pueblo, Taos County, New Mexico. Prepared by USBIA, Southwest Regional Office (SWRO), Branch of Water Rights, Geohydrology Section. Prepared for Proposal for Technical Studies Conducted to Assist Settlement Discussions in the NM v. Abeyta, Drilling Program, Pueblo Portion, March USBIA, 2003, U.S. Bureau of Indian Affairs, BOR 7 Site Completion Report for the Pueblo Portion at Taos Pueblo, Taos County, New Mexico. Prepared by USBIA, Southwest Regional Office (SWRO), Branch of Water Rights, Geohydrology Section. Prepared for Proposal for Technical Studies Conducted to Assist Settlement Discussions in the NM v. Abeyta, Drilling Program, Pueblo Portion, March

33 USBOR, Summary of Discharge Measurements Performed on Taos Valley Streams and Canals in 1983, 1989, 2000, and Denver Technical Center, February USGS, 2000, United States Geological Survey Ground-Water Site Inventory (USGS GWSI). Wilson, B.C. and M. Smith, 2004, Taos Pueblo and Rio Pueblo de Taos drainage basin, Taos County, New Mexico; Quantification of Irrigation Water Requirements. OSE Memorandum dated 2/13/2004. Wilson, L., Anderson, S.T., Jenkins, D.N., and Lovato, P., 1978, Water availability and water quality, Taos County, New Mexico: Consultant report prepared for the Taos County Board of Commissioners by Lee Wilson and Associates, Inc., Santa Fe, New Mexico. 27

34 Pueblo Arizona Utah Colorado Farmington New Mexico Gallup Durango Rio Rancho Albuquerque Santa Fe R io Grande Taos Las Vegas Ok. Texas Grande Los Lunas Hereford Rio Portales Clovis Roswell Levelland Silver City Alamogordo Artesia Deming Las Cruces Carlsbad Hobbs Sunland Park Midland Odessa Rio Grande M E X I C O Taos Model Location É Miles 28

35 Figure 2. Observed Water Level Contour Map, contour elevations given in feet amsl (after Spiegel and Couse, 1969; and Purtymun, 1969). Also shown: locations of key wells. 29

36 Figure 3. Model Grid and Selected Model Boundary Features. Numbered Cells Represent MODFLOW STR Segments. 30

37 column Diagram of STR Reach Numbers. OSE Taos Model T17.0 Uppermost Active Layer Split between 1 and 16 designates location of last diversion on Rio Hondo 1 Reach 1 5 Simulated Split between 14 and 15 designates location of last diversion on Rio Pueblo de Taos Number 3 6 Faults row

38 Figure 5. Schematic Cross-Section of the Taos Valley Showing Geologic Layers Represented in the Taos Regional Groundwater Model. Layer Thickness information provided in Table 2. 32

39 Cross Section of Model Layers, OSE Taos Groundwater Model T17.0, 2004 East Taos Pueblo Rio Grande Layer 4 Layer 1 Layer 2 Layer 3 Layer 5 - Basalts Layer 6 Layer 7 Land Surface Elevation Water Table (Spiegel and Couse, 1969) Distance (miles) Elevation (feet amsl)

40 Cross Section of Model Layers, OSE Taos Groundwater Model T17.0, 2004 Taos Pueblo Rio Grande East Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 - Basalts Layer 6 Land Surface Elevation Layer 7 Water Table (Spiegel and Couse, 1969) Distance (miles) 34 Elevation (feet above MSL)

41 residuals-17updated.xls 5/23/2005 2:36 PM Calibration Results: Taos Groundwater Model version T17.0 1/04 Observed vs. Simulated Heads All Layers Model Simulated Heads Observed Heads (feet above means sea level) 35

42 /23/2005 residuals-17updated.xls Calibration Results Taos model T17 1/04 Frequency Distribution of Residuals A negative residual indicates that simulated values are too high < to to to to to to to to to to 0 0 to to to to to to to to to to 100 >100 Range of Residual (ft) 36 Frequency

43 Location Map for Vertical Hydraulic Gradient Data model: columns Well Location on Model Grid row Rio Hondo Arroyo Seco Cielo Azul 13 Rio Lucero BOR 7 17 Grumpy BOR 4/BOR 6 BOR Buffalo Pasture Rio Pueblo 34 de Taos Karavas 2/Karavas 3 38 Taos Town Wells Rio L97/ L91 42 Grande 43 Rio 44 Fernando 45 Taos Yard BOR 2/ BOR 3 48 Rio Pueblo L25/ L Rio Grande 54 Rio Pueblo del Rancho 55 de Taos BOR 1/ National Guard 58 Rio Chiquito

44 APPENDIX A Water Level Data Used for Calibration of Taos Groundwater Model T17.0 Water level data compiled by OSE personnel from a variety of sources: U.S. Geological Survey (USGS) Ground-Water Site Inventory (GWSI) (Source ID: A##) Office of the State Engineer Well Records (including WATERS database) (Source ID: D##) Bauer et al. (1999) (Source ID: B##) Garrabrant (1993) (Source ID: G##) Glorieta Geoscience, Inc. Reports (Source ID: GG##) Lee Wilson and Associates, Inc. Report (1978) (Source ID: L##) Taos Pueblo Well Inventory (Source ID: P##) Purtymun (1969) (Source ID: Y##) Well locations for many wells were derived from PLSS or other data using GIS techniques. Row, column and offset values designated in red were adjusted to place observation at the center of cells located at edge of active model domain, in order to permit MODFLOW-2000 to calculate residuals. Row, column and offset values designated in blue were estimated based on available PLSS data. Appendix A page 1

45 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation OW-9 Shallow P40 P OW-9 Deep P39 P West Well - BIA-19 P21 BIA Acequia Well - BIA 12 P13 BIA OW-1 P29 P OW-8 P38 OW MW-2 P30 P RG L194 L MW-4 P32 P MW-3 P31 P OW-5-shal P34 OW5S OW-5-deep P33 OW5D OW-6-shal P36 OW6S OW-6-deep P35 OW6D OW-7 P37 OW RG L202 L RG-3465 L197 L RG-3464 L198 L RG L41, Archuleta L RG D474 D Hail Creek Shallow - BIA 22 P24 P BIA Y5 Y RG L81 L Antonio Romero Y11 Y RG-2045 L69 L RG L99 L RG-371 L90 L RG-5407 L97 L RG L87 L RG-5422 L122 L RG L191 L South Well Shallow - BIA 16 P18 P RG D401 D RG-3370 L192 L RG L199 L RG L42 L RG L49 L RG L51 L RG L46 L RG-5773 L45 L RG L52 L RG L57 L RG L56 L Total Depth pbarroll HOBS-7L.xls lpage 1 10/28/2005 Appendix A page 2

46 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation RG L68 L Ann Barlow Y8 Y RG L77 L RG L71 L RG L70 L A2/G12 A RG-8633 L82 L RG L80 L RG D553 D RG L83 L RG D576 D RG D584 D RG-3419 L121 L RG-2950 L93 L RG D617 D RG D621 D RG L114 L RG-9794 L123 L RG D628 D RG D116 D RG D119 D RG D128 D RG L168 L A3/G19 G RG D229 D RG-6410 L166 L RG D240 D RG-7146 L169 L RG L170 L RG D270 D RG-6207 L162 L RG Cielo Azul GG3 GG RG L171 L North Well - BIA 18 P20 BIA RG L178 L Grumpy Well Shallow - BIA 25 P27 BIA Mid-Point Well - BIA 17 P19 BIA RG L180 L RG D316 D RG L179 L RG D325 D RG D326 D RG-1828X L185 L Total Depth pbarroll HOBS-7L.xls page 2 10/28/2005 Appendix A page 3

47 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation OW-10 P41 P RG D337 D RG-7239 L181 L RG-1828-S L186 L RG-1828-REPLACE L187 L RG-9359 L183 L RG D356 D RG D354 D RG D357 D RG-1828 L184 L RG D363 D RG D364 D RG D365 D RG-1822 L182 L RG-1828-A-S/RG X D359/D360 D A19/G20 A Ski & Tennis Ranch GG4 GG RG L188 L RG Colonias Point GG2 GG RG-7955 L190 L Acequia Well - BIA 13 P14 P South Well Deep - BIA 16 P17 P RG-3255 CLW L189 L RG D424 D RG D425 D RG L196 L to A29/G18 A RG L193 L RG D448 D RG L195 L RG L44 L Taos Pueblo Comm. Bldg. Y12 Y RG D459 D BIA Y1 Y BIA Y2 Y RG-5150 L54 L RG D473 D RG-5977 L55 L RG L58 L RG A15/G10 A RG Ceja de Colonias D Hail Creek Deep - BIA 21 P23 P RG D493 D Total Depth pbarroll HOBS-7L.xls Page 3 10/28/2005 Appendix A page 4

48 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation Don's OW P28 P NA RG-7339-S-5 Howell Taos 6 GG15 Taos A8/G11 A RG Chatwin chat Karavas 1 P44 K Karavas 2 screen 7 P49 K Taos Cerro Project; OP-TP-1A L76 L RG D520 D RG L84 L RG-7339-S2 / A4/G13/Taos 3 Taos Clinic Well - BIA 1 P1 P RG-12138/Upper Ranchitos MD L59 L RG-7339 / A10, Town Well 1 Taos RG-7339-S / A7/G14 Taos Niche Well - BIA 23 P25 BIA Clinic Well - BIA 1 P1 BIA Tribal Well RWP-6, BIA 3 P3 BIA RG Cooper GG1 GG RG Kit Carson KC RG-7339-S4 Taos #5 L95/B33 Taos A31/G5 A RG-482 L91 L RG L88 L RG Arroyo Park GG9 D58 D RG L100 L RG-20081; Taos Cerro Project; DH-T6 L85 DH-T RG D596 D RG L124 L RG D623 D RG-5673 L98 L RG L86 L RG D625 D RG L131 L Owner Record B55 B RG B22 B RG L113 L RG D626 D RG D630 D RG L118 L RG D634 D RG B21 B RG D648 D RG D662 D Total Depth pbarroll HOBS-7L.xls Page 4 10/28/2005 Appendix A page 5

49 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation Driller B49 B RG B15 B RG B13 B RG L116 L RG L111 L RG L115 L RG L119 L RG L125 L RG L132 L RG D674 D A27/G7 A BOR2-a BOR2-A BOR2A RG L112 L RG-48434X D673 D RG-402 L120 L RG D686 D RG D679 D RG D687 D RG L133 L RG B56 B RG L117 L RG D693 D RG L24 L A26/G8 A RG L138 L RG D714 D RG D713 D RG L142 L RG D744 D RG-5846 L28 L RG L27 L RG L25 L RG L26 L RG D750 D RG D746 D RG L141 L RG L143 L RG L144 L B67/A21/G15 A GGI B9 B RG D779 D RG D776 D RG La Fontana D773 D Total Depth pbarroll HOBS-7L.xls Page 5 10/28/2005 Appendix A page 6

50 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation RG D774 D RG-1756 / Ranchos de Taos MD L137 L RG L139 L RG D765 D RG D759 D RG D754 D RG L140 L RG B28 B RG B29 B RG D789 D RG B54 B RG B53 B Driller B42 B RG B51 B RG B50 B RG B38 B RG B3 B RG D827 D RG B2 B RG D839 D RG B62 B RG L39 L A22/G9 A RG B59 B RG L40 L RG L145 L RG L148 L RG D907 D Owner B46 B RG D920 D RG L32 L RG B8 B RG L35 L RG D948 D RG D958 D A18/G3/B66 A Driller B40 B RG D967 D RG D966 D RG B12 B RG-3894-S / Llano Quemado MD B58 B RG D983 D RG-7462 L10 L Total Depth pbarroll HOBS-7L.xls Page 6 10/28/2005 Appendix A page 7

51 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation RG-6539 L9 L A25/G2 A RG-4995 L6 L D987 D RG D1001 D RG-61059CLW & RG D996/D997 D RG D76 D RG D87 D RG-7609 CLW / Upper Arroyo Hondo ML206 L RG D156 D RG / Lower Des Montes MD L207 L RG D279/W_1358 D Tract B Tip Well - BIA 10 P11 BIA Tract B Tip Well - BIA 11 P12 BIA BOR 4 BOR 4-S BOR4S RG D388 D RG D384 D TP-2 Taos North BOR tp RG A28/G16 A RG Cameron CAM Buffalo Pasture Well - BIA 2 P2 P Don's Well - BIA 14 P15 BIA Taos Cerro Project; OH-TP-1B L48 L Karavas 2 screen 6 P48 K RG La Percha GG11 GG Tract A PW2 - BIA 15 P16 BIA RG-7339-S3; Taos #4 L94 Taos RG-7339X-S B32 B RG B16 B RG B23 B RG B47 B RG-50762X B48 B RG D657 D RG L29 Sewage treatmen Sew RG B10 B RG B6 B RG D751 D RG B7 B RG B4 B Driller B39 B RG D770 D Driller B52 B RG / BOR 1 Shallow BOR1 Shallow GG13 BOR1S Total Depth pbarroll HOBS-7L.xls Page 7 10/28/2005 Appendix A page 8

52 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation RG B1 D RG D980 D RG B19 B River View Acres test well RVA R12E Sec 6 SW 1/ RG D176/W_1302 D RG Mariposa Ranch GG7 MAR RG D263/W_1283 D RG D288/W_1331 D RG D291/W_1357 D RG D303/W_1334 D Tract B OW - BIA 7 shallow P8 BIA7s Tract B PW2 - BIA 9 P10 BIA Grumpy Well - BIA 24 P26 BIA RG D318/W_1336 D RG D328/W_1342 D RG-4066 L150 L West Deep Well - BIA 20 P22 BIA RG Taos Landfill TL RG EXP El Prado Wtr & San ELPR Karavas 2 screen 5 P47 K Taos Yard Exploratory Deep GG17/B61 TY RG A33/G6 Exploratory A RG / RG EX Taos SJC GG10 SJC Special OSE file L30 L RG Riverbend RIVB RG BJV1 GG5 GG RG EXP Barranca del Pueblo BAR RG EX UNM/Taos GG6 UNM Tract B OW - BIA 7 Deep P7 BIA7d Tract B PW - BIA 8 P9 BIA BOR 5 BOR 5 BOR Taos Airport deep TA Karavas 2 screen 2 P46 K Tract A OW - BIA 5 P5 BIA Tract A PW - BIA 6 P6 BIA RG BOR 2B intermediate BOR2B Rio Pueblo 2000 upper RP2Ku RG Nat Guard Domestic NG RG BOR1 deep BOR BOR 7 BOR 7 BOR BOR 6 BOR 6 BOR BOR 4 BOR 4-D BOR4D Karavas 2 screen 1 P45 K Total Depth pbarroll HOBS-7L.xls Page 8 10/28/2005 Appendix A page 9

53 Table A1 Well ID Well ID Source ID Water Level Data Used as Targets for the Taos Groundwater Model Well Location Model Coordinates MODFLOW Target ID X UTM NAD83 Y UTM NAD83 Model Layer Row Col Row offset Col offset Elevation/Depth data in feet Ground Surface Elevation Depth to Water Water Level Elevation Karavas 3 P50 K RG BOR 2C deep BOR2C BOR 3 BOR 3 BOR Rio Pueblo 2000 deep RP2Kd Rio Pueblo 2000 middle RP2Km RG Rio Pueblo 2500 RP25K Total Depth pbarroll HOBS-7L.xls Page 9 10/28/2005 Appendix A page 10

54 APPENDIX B Distribution of Hydraulic Properties, Stresses and Calibration Residuals for Taos Groundwater Model T17.0 This Appendix contains the following model information: 1) Hydraulic Conductivity (K) Diagrams, Layers 1 through 7 2) Transmissivity (T) Diagrams, Layers 1 through 7 3) Distribution of Irrigation Return Flow (Groundwater Accretions from Irrigation) 4) Distribution of Mountain-Front Recharge 5) Table Summarizing Well Pumping Simulated in Model 6) Distribution of Municipal, Domestic and Sanitary Pumping Diagrams 7) Calibration Residuals Diagrams, Layers 1 through 7 All diagrams were generate using Microsoft Excel for illustrative purposes, and are not to scale, and generally have some horizontal exaggeration. Model cells are actually squares: ¼ mile by ¼ mile. Row values are listed along the left hand side, and column values are listed along the top of each diagram. These diagrams include a few basic model features. RIV and STR cells that represent the Rio Grande and its tributaries are designated by bordered cells. The Buffalo Pasture is denoted by bordered STR cells with pink font within. The background colors of the cells indicate which layer contains the uppermost active cell at each x, y location for the model as a whole. Light Blue Cells: the uppermost active cells are in layer 1. Yellow Cells: the uppermost active cells are in layer 3 (layers 1 and 2 are not active in these locations) Orange Cells: The uppermost active cells are in layer 4 (layers 1, 2 and 3 are not active in these locations) Green Cells: The uppermost active cells are in layer 5 (layers 1, 2, 3 and 4 are not active in these locations) White cells: Only the white cells representing the Rio Grande, which are the bordered white cells along the left hand side of the active model grid, are active. These cells are in layer 6. Appendix B page 1

55 Layer 1 Hydraulic Conductivity (ft/day) K Appendix B page 2

56 Layer 2 Hydraulic Conductivity (ft/day) K Appendix B page 3

57 Layer 3 Hydraulic Conductivity (ft/day) K Appendix B page 4

58 Layer 4 Hydraulic Conductivity (ft/day) K Appendix B page 5

59 Layer 5 Hydraulic Conductivity (ft/day) Layer 5 Hydraulic Conductivity (ft/day) K Appendix B page 6

60 Layer 6 Hydraulic Conductivity (ft/day) Layer 6 Hydraulic Conductivity (ft/day) K Appendix B page 7

61 Layer 7 Hydraulic Conductivity (ft/day) Layer 7 Hydraulic Conductivity (ft/day) K Appendix B page 8

62 T1 Column: T17.0 Transmissivity Layer 1 ft2/day Row Appendix B page 9

63 T2 Column: T17.0 Transmissivity Layer 2 ft2/day Row: Appendix B page 10

64 T3 Column: T17.0 Transmissivity Layer 3 ft2/day Row: Appendix B page 11

65 T4 Column: T17.0 Transmissivity Layer 4 ft2/day Row: Appendix B page 12

66 T5 Column: T17.0 Transmissivity Layer 5 ft2/day Row: Appendix B page 13

67 T6 Column: T17.0 Transmissivity Layer 6 ft2/day Row: Appendix B page 14

68 T7 Column: T17.0 Transmissivity Layer 7 ft2/day Row: Appendix B page 15

69 Zones of Irrigation Return Flow Application Averagcol row Application of Irrigation Return Flows to Groundwater Zone Number Zonal Application Rate (AF/yr) Location Description of Zone A - NW of Rio Hondo B - NE of Rio Hondo C - SW of Rio Hondo D - BTW RH & AS E - West Side of AS F - South Side of AS G - Btw AS & RL H - Btw RL & RPdT I - Btw RPdT & RFdT J - South Side of RFdT K - East Side of RGdR & RC L - West Side of RGdR M - North Side of RPdT Appendix B page 16

70 Diagram of Mountain Front Recharge Distribution T17.0 Averaolumn row Mountain Front Recharge Zone Number Distribution Zonal Recharge Rate (AF/yr) Appendix B page 17

71 Well Pumping Input into Calibration Run of T17.0 Model (AF/yr) Stress Period: Taos Pueblo* Town of Taos El Prado Other Mutual Domestic Wells Domestic Well* Multiple Dwelling Domestic Wells* Sanitary Wells* Total * Estimated Diversions Appendix B page 18

72 Rows olumns 1 Lo bo Creek Sou th Fork Rio Hondo 5 10 Lower Arroyo Hondo Upper Arroyo Hondo Rio Hondo Valdez Upper Desmontes (1) Lower Desmontes Upper Desmontes (2) Arroyo Seco El Salto El Prado (3) R io Grande El Prado (2) de Rio Pueblo Taos 40 Upper Ranchitos 45 Rio Fernando de Taos Canon (2) Canon (1) Arroyo Alamo Talpa (4) Llano Quemado (2) Llano Quemado (1) R Ranchos de Taos (1) Ranchos de Taos (2) Talpa Talpa io Grande del Rancho Arroyo Hondo Miles Taos Mutual Domestic Wells and El Prado WSD Wells Appendix B page 19

73 Municipal and Other Non-Domestic Water Supply Wells Simulated in Taos Groundwater Model AveColumn Row Designation Wells 1 Taos Pueblo (estimated, generalized pumping location) 2 Town of Taos 3 El Prado Water & Sanitation District 4 Mutual Domestic Associations Appendix B page 20

74 Distribution of Domestic Wells and Sanitary Type Wells Simulated in Taos Groundwater Model Includes wells listed in OSE files as Domestic, Multiple (Domestic well serving multiple dwelling) and Sanitary Numbers shown represents the number of these types of wells that occur in the model cells SumColumn Row Appendix B page 21

75 t17-0-resids.xls 1/4/200612:43 PM T-17 Calibration Results Layers 1, 2 and 3 Residuals (Observed - Modeled Heads) in feet Sum -129 Average -1 row 6789###### # # # Appendix B page 22

76 t17-0-resids.xls 1/4/ :44 PM T-17 Calibration Results Layer 4 Residuals (Observed - Modeled Heads) in feet Sum 295 Average 10 row Appendix B page 23

77 t17-0-resids.xls 1/4/2006 T-17 Calibration Results Layer 5 Residuals (Observed - Modeled Heads) in feet Sum 61 Average 3 Ave col row Appendix B page 24

78 t17-0-resids.xls 1/4/2006 T-17 Calibration Results Layer 6 Residuals (Observed - Modeled Heads) in feet sum -12 average -1 row Appendix B page 25

79 t17-0-resids.xls 1/4/ :45 PM T-17 Calibration Results Layer 7 Residuals (Observed - Modeled Heads) in feet Sum -83 Average -14 row Appendix B page 26

80 Appendix C Detailed hydrogeologic background report: Hydrologic Characteristics of Basin-fill Aquifers in the Southern San Luis Basin, New Mexico By Paul Drakos, Jay Lazarus, Bill White, Chris Banet, Meghan Hodgins, Jim Riesterer and John Sandoval. New Mexico Geological Society Guidebook, 55 th Field Conference, Geology of the Taos Region, 2004, p Appendix C page 1

81 New Mexico Geological Society Guidebook, 55 th Field Conference, Geology of the Taos Region, 2004, p HYDROLOGIC CHARACTERISTICS OF BASIN-FILL AQUIFERS IN THE SOUTHERN SAN LUIS BASIN, NEW MEXICO PAUL DRAKOS 1, JAY LAZARUS 1, BILL WHITE 2, CHRIS BANET 2, MEGHAN HODGINS 1, JIM RIESTERER 1, AND JOHN SANDOVAL 2 1 Glorieta Geoscience Inc. (GGI), PO Box 5727, Santa Fe, NM US Bureau of Indian Affairs (BIA), Southwest Regional Office, 615 First St., Albuquerque, NM ABSTRACT. The Town of Taos and Taos Pueblo conducted a joint deep drilling program to evaluate the productivity and water quality of the Tertiary basin-fill aquifer system underlying the Servilleta Formation. Testing results from a series of municipal, exploratory, subdivision, and domestic wells are also used to characterize hydrologic properties (T, K, K, and S), and the effect of faults on groundwater flow in shallow and deep basin fill aquifers. The shallow unconfined to leaky-confined alluvial aquifer includes alluvial deposits and the underlying Servilleta Formation (Agua Azul aquifer facies). The deep leaky-confined to confined aquifer includes Tertiary age rift-fill sediments below the Servilleta Formation and is subdivided into the Chama-El Rito and Ojo Caliente aquifer facies. Although faults typically do not act as impermeable boundaries in the shallow alluvial aquifer and groundwater flow in the shallow aquifer is not significantly affected by faults, the Seco fault and several of the Los Cordovas faults act as impermeable boundaries in the deep basin fill aquifer. However, other Los Cordovas faults apparently do not affect groundwater flow in the deep aquifer, suggesting variable cementation along fault planes at depth. The Town Yard fault appears to be a zone of enhanced permeability in the shallow alluvial aquifer, and does not act as an impermeable boundary in the deep basin fill aquifer. Intrabasin faults such as the Seco fault that exhibit significant offset likely cause some compartmentalization of the deep aquifer system. INTRODUCTION The Town of Taos, Taos Pueblo, and adjacent communities are situated primarily within the Rio Pueblo de Taos and Rio Hondo drainage basins. The Rio Pueblo de Taos basin includes the following streams from north to south; Arroyo Seco, Rio Lucero, Rio Pueblo de Taos, Rio Fernando de Taos, and Rio Grande del Rancho (Figs. 1 and 3). Northern tributaries to Rio Pueblo de Taos drain Precambrian granite and gneiss, and Tertiary granite, whereas southern tributaries drain Paleozoic sandstone, shale, and limestone (Kelson and Wells, 1989). The area of this study includes the region between the Sangre de Cristo mountain front on the east and the Rio Grande on the west, the Rio Hondo on the north and the Rio Grande-Rio Pueblo de Taos confluence on the south (Fig. 1). The majority of the historic water supply for municipal, domestic, livestock, and sanitary purposes for the Town of Taos, Taos Pueblo, and adjacent communities has been derived from the Colorado Plateau Mogollon - Datil Volcanic Field Jemez Volcanic Field Jemez Lineament P S M A Rio Grande Rift E SL Southern Rocky Mountains Study Area Great Plains Kilometers Symbol 1 1 Rio Grande Explanation Major stream or river Miles 1 Kilometers US Hwy 64 Rio Pueblo detaos State Rd. 68 Rio State Rd. 68 Hondo Town of Taos Study Area Detail FIGURE 1. Location map schematic map of New Mexico showing study area and the approximate limits of various physiographic provinces and geographic features. Major basins in the Rio Grande rift from north to south are: SL=San Luis, E = Española, A = Albuquerque, S = Socorro, P = Palomas, M = Mimbres. (state map modified from Sanford et al., 1995 and Keller and Cather, 1994). Hwy. 150 US Hwy 64 Sangre de Cristo Mountains Appendix C page 2